Lecture_10 - Earth's Energy Budget 1.0 Factors driving...

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Earth’s Energy Budget 1.0 Factors driving natural climate change Plate Tectonics – position of continents through geologic influence climate at specific locations as well as globally by redistributing absorbed short-wave radiation and providing land masses on which continental glaciers form. e.g. During much of the “warm” Mesozoic the world's continents were joined into the supercontinent of Pangea centered on the equator. Orbital Variability Eccentricity – ~100,000 yr period. Presently, Earth’s orbit nearly circular but in 50,000 years will be more eccentric with difference between aphelion (farthest) and perihelion (nearest) larger. More eccentric means cooler summers and winters in both northern and southern hemispheres. Obliquity – ~41,000 year period. Presently, Earth’s tilt ~23.5 ° but because of wobble changes between ~22.5 and ~24.5. Greater tilt means warmer summers and colder winters in both northern and southern hemispheres. Precession of Equinox - ~23,000 year period. Presently, Earth closest to Sun in January and farthest in July resulting in warmer winters and cooler summers in northern hemisphere. Time of year when Earth reaches perihelion however precesses due to wobble such that in 11,500 years perihelion will be in July. Perihelion in July means colder winters and warmer summers in northern hemisphere and warmer winters and colder summers in southern hemisphere. Volcanic Eruptions – cycles of volcanic eruptions and introduction of greenhouse gasses such as CO 2 and H 2 O through geologic time influence climate by trapping long-wave radiation. Also, emitted SO 2 reacts in upper parts of atmosphere to form small sulfate particles that reflect short-wave radiation. e.g. Eruption of Mt. Pinatubo in 1991 introduced 20 million tons of SO 2 into stratosphere resulting in a
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average global temperature drop of 0.2-0.5 ° C for a period of 1-3 years.
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Lecture_10 - Earth's Energy Budget 1.0 Factors driving...

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